I have been driving a Chevy VOLT for a year and a half. I have more than 26,000 miles on it, and have used 100 gallons of gasoline. That works out to more than 250 mpg. Of course, I have been charging the VOLT at home every night, and at the office during the day but my electric bills at both places are not noticeably higher. It would be nice if the electric range were a bit longer, but the gasoline engine on board that charges the batteries guarantees that I can keep driving as long as I need to.

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What are the limiting factors to increasing the range of the lithium ion batteries? Researchers led by Ohio State University engineers examined used car batteries and discovered that over time lithium accumulates beyond the battery electrodes — in the "current collector," a sheet of copper which facilitates electron transfer between the electrodes and the car's electrical system.

This knowledge could aid in improving design and performance of batteries, explained Bharat Bhushan, Ohio Eminent Scholar and the Howard D. Winbigler Professor of Mechanical Engineering.

"Our study shows that the copper current collector plays a role in the performance of the battery," he said.

The study, which appears in a recent issue of the journal Scripta Materialia, reflects an ongoing collaboration between Bhushan and Suresh Babu, professor of materials science and engineering and director of the National Science Foundation Center for Integrative Materials Joining for Energy Applications, headquartered at the university. The team is trying to determine the factors that limit battery life.

Lithium-ion batteries are the rechargeable batteries used in most hybrid-electric cars and all-electric cars as well. Inside, lithium ions shuttle back and forth between the anode and cathode of the battery — to the anode when the battery is charging, and back to the cathode when the battery is discharging.

Previously, the researchers determined that, during aging of the battery, cyclable lithium permanently builds up on the surface of the anode, and the battery loses charge capacity.

This latest study revealed that lithium migrates through the anode to build up on the copper current collector as well.